1. Field of the Invention
The present invention relates to a mounting device for a local gradient coil unit for mounting thereof in a gradient coil system.
2. Description of the Prior Art
Magnetic resonance devices have been used for a considerable time in medicine and in biophysics for obtaining images from inside the body of an examination subject. Magnetic resonance tomography is based on the physical phenomenon of nuclear magnetic resonance. In this examination modality, the examination subject is exposed to a strong, constant magnetic field, causing the previously irregularly oriented nuclear spins of the atoms become aligned in the examination subject. Radio-frequency energy is used to excite these disordered nuclear spins to produce a particular oscillation (resonant frequency). In resonance tomography, this oscillation generates the actual high-frequency measurement or response signal for the imaging process. Reception coils are provided for receiving the measurement or response signal.
A prerequisite for image generation is precise information about the respective place of origin of the measurement or response signal in the examination subject. Location information or a location coding for the received measurement or response signals is required. This location information is obtained by using additional magnetic fields, so-called gradient fields. The gradient fields are generated using a gradient coil system along the three spatial directions of individual gradient coils. The gradient field superimposed on the basic field is such that the field strength and thus also the resonant frequency is different in each volume element. The basic structure and the function of a magnetic resonance system are adequately known.
The use of a local gradient coil unit is known for the examination of special areas of an examination subject, the head for example. This is incorporated into the permanently installed gradient coil system. To this end, it is possible to use an insertion device, as is described in the German patent application DE 102 29 489 A1. This device described therein has an arm arranged either on a transport carriage or a swivel mount, on which is located the gradient coil unit to be inserted, frequently also referred to as insert gradient coil. The arm travels into the examination area of the magnetic resonance unit, which is the gradient coil system in this case, which is usually provided with a lining on the inside wall, until the arm has reached a defined position. Depending on the embodiment, the arm can now remain in the examination area and it serves to secure the gradient coil unit during the examination. Alternatively, it is also possible after reaching the end position to use suitable attachment facilities provided in the examination area to attach the gradient coil unit, to release it from the arm and to retract the arm again.
This insertion or mounting device is relatively complex in design, since the arm must be adequately dimensioned because a local gradient coil unit can have a considerable weight and it sometimes needs to be supported over a considerable length until the end position is reached.